package com.itheima;

public class Demo {
    public static void main(String[] args) {
        //null : 空常量,不能直接输出打印
        //System.out.println(null);

        // null是引用数据类型的默认值,可以给任意引用数据类型变量赋值
        String s = null;
        System.out.println("s = " + s);

        s = "abc";
        System.out.println("s = " + s);

        System.out.println('我');

        int a = 10;
        System.out.println("a = " + a);

        a = 20;
        System.out.println("a = " + a);


        //float b = 3.14F;
        float b = 3;     // 自动类型转换. jvm底层会自动把3提升为3.0 然后再3.0后面加个f
        System.out.println("b = " + b);

        long l = 10000000000L;
        System.out.println("l = " + l);


        int x = 10;

        {
            x = 20;
            System.out.println(x);
        }
        System.out.println(x);
    }
}
